Dispensing of hazardous liquids such as acids and other corrosive liquids must be achieved carefully to avoid spillage of liquid and to avoid the user of a dispenser having liquid contact the user's skin. Pouring liquids from a container such as a bottle can result in drips, either dropping beside the bottle or running down the outside surface. If this happens, then the liquid can contact the skin of a user. Thus, it is always necessary to clean up after any corrosive liquid has been dispensed to ensure no drops are left on or around the container.
It is also a requirement to be able to dispense a predetermined quantity of liquid accurately from one container to another vessel without contamination of the dispensed liquid. There are a number of dispensing devices available today, however, it is most important that there is no flow back of the liquid once it has been withdrawn from a container, otherwise this can cause contamination in the supply container.
Rolph in U.S. Pat. No. 1,929,564 discloses a manual pump for delivering measured quantities of liquid, as does Pfeiffer et al in U.S. Pat. No. 4,565,302. However, neither of these patents address the problem of preventing contamination.
It is an object of the present invention to provide a device for withdrawing a precise amount of liquid from a supply container and transferring this precise amount to another vessel without contamination of the dispensed liquid or the remainder of the liquid in the container. Another object of the invention is to maintain the safety of the operator by lessening the chances of minor drips or major spills of hazardous liquids occurring. A still further object of the invention is to perform all of the required actions with only one hand in order to leave the other hand free and without moving the liquid container.